The present disclosure relates to a fixing device for use in image forming apparatuses such as a copier, a printer, a facsimile, and a multifunction peripheral having these functions, and to an image forming apparatus including the same. In particular, the present disclosure relates to a fixing device that employs a belt fixing method in which a sheet carrying an unfixed toner image thereon is passed through a fixing nip portion, which is formed by a heated fixing belt and a pressure member, and unfixed toner is heated and melted to be fixed on the sheet.
For conventional image forming apparatuses employing the electro-photographic method, there has been developed a belt fixing method in which, instead of a heating roller, an endless fixing belt that absorbs radiant heat from a heat source to liberate heat is employed as a heating member for heating a sheet. According to the belt fixing method, a sheet carrying an unfixed toner image is passed through a fixing nip portion formed by the heated fixing belt and a pressure member, which is pressed against the fixing belt, and thereby toner is fixed onto the sheet.
With the belt fixing method, it is possible to reduce thermal capacity and shorten a warm-up period to thereby reduce power consumption, as compared with a case of adopting a heat roller fixing method in which at least one of a pair of fixing rollers forming a fixing nip portion is used as a heating roller, and a sheet carrying an unfixed toner image is passed through the fixing nip portion to thereby fix toner onto the sheet.
For example, there is known a fixing device that includes a fixing member that is a rotatable endless belt, a pressure member so disposed on an outer circumferential side of the fixing member as to be able to be pressed against the fixing member, a nip forming member that is disposed at an inner circumferential side of the fixing member, that is formed of a base member and a sliding sheet wound around the base member, and that is pressed against the pressure member via the fixing member to form a nip portion, a reinforcement member fixed to an inner diameter portion of the fixing member to support the nip forming member from a side opposite to the nip portion, a substantially cylindrical support member fixed to the inner circumferential side of the fixing member such that an outer circumferential surface of the support member is in slide contact with an inner circumferential surface of the fixing member to support rotation of the fixing member, and heating means that is disposed inside the cylindrical support member and heats the support member.